CRETACEOUS AND TERTIARY FORMATIONS, n 



the Magothy, Woodbury and Wenonah are absent. The forma- 

 tion has a maximum thickness of about 40 feet, diminishing 

 southward to 25 feet or less. It corresponds in general to Cook's- 

 Lower Marl, although locally beds referred by him to the Lower 

 Marl have proved to be the Marshalltown. It rests conformably 

 upon the beds below and grades upward into the Red Bank sand, 

 or where that is absent into the Hornerstown marl. 



Red Bank sand. — The Red Bank sand is for the most part a 

 fairly coarse ferruginous yellow and reddish-brown quartz sand, 

 locally indurated by the infiltration of iron. The lower beds are 

 in many places somewhat clayey. The Red Bank invertebrate 

 fauna has come chiefly from these clayey layers. In its essential 

 features it is a recurrence of the Lucina cretacea fauna of the 

 Magothy, Woodbury and Wenonah formations, and differs in 

 important respects from the Navesink fauna immediately below. 

 It occurs only in the northern part of the coastal plain, where its 

 maximum thickness is 100 feet, but it thins out and disappears 

 midway across the State. It is the Red Sand of Cook and earlier 

 writers, but does not include certain sands in the southern portion 

 which were correlated by him with the Red Sand of Monmouth 

 county, but which in reality are referable to the Wenonah-Mt. 

 Laurel horizon. With the overlying Tinton bed, it is the upper- 

 most of the beds correlated with the Monmouth formation of 

 Maryland. 



Tint on bed. — <A lense of green indurated clayey and sandy 

 marl, having a thickness of from 10 to 20 feet, overlies the Red 

 Bank sand in Monmouth County. Its invertebrate fauna is more 

 closely allied to that of the Navesink than of the Red Bank and 

 is characterized by large numbers of crustacean claws of the 

 genus Callianassa. It is Cook's "indurated green earth," re- 

 garded by him and other writers as a part of the Red Sand, but 

 in view of its faunal and lithologic differences it deserves some 

 separate recognition. 



Correlation of the Magothy-Tinton beds. — The assemblage of 

 fossils making up the invertebrate faunas of the beds from the 

 Magothy to the Tinton inclusive constitute a larger faunal unit, 

 much more sharply separated from the faunas above and below 



